Adventures in TinyAVR 1-Series

HQ, without checking into each specific pin, what you have laid out looks correct. There are many pins capable of PWM. Almost any pin can be used for ADC. Any pin can be used for Aux & Switch (well, outside of VDD, GND, and UPDI/Reset).

Side note about voltage sensing: you can directly sense voltage from the VDD pin with good accuracy, assuming you don’t have an LDO in front of it. Whereas the attiny85’s internal VREF was +/- 10, the 1-Series VREF is +/- 2.

Side note 2: also unlike the attiny85, the 1-Series chips have factory-calibrated temp sensing. The factory calibrated values (slope and offset factors) are stored in TEMPSENSE registers and seem to be pretty accurate.

And TK is (of course!) spot on. Going to a higher resolution PWM can be nice, but it doesn’t necessarily fix things in the low end of the spectrum because of the length of time that some of these chips (like the AMC7135) need to be turned on to function properly.

I like where you were going TK with the resistor for smoothing out the ramp. Slightly different, but I’ve seen a few drivers lately that use a resistor for their moonlight channel (non-PWM).

Another option would be to add an adjustable linear regulator like one of these:

  • AMC7136 (10mA - 400mA, internal FET)
  • QX7138 (20mA - 3A, external FET)
  • CN5710 (60mA - 1A, internal FET)
  • OC7141 (10mA - 3A, external FET)

In addition to being able to PWM these chips, you could employ a FET that effectively adds/removes resistance on the current sense pin to vary the current that it’s controlling to. That would allow us to use a single linear regular with varying levels of current output even before you start PWM’ing the thing (you could vary the current sense resistor AND use PWM to get a wide range of effective currents). This is nicely illustrated in the CN5710 datasheet

@gchart
Thanks, that is quite assuring.

I don’t use ADC for voltage monitoring on the 85 anymore. But there was recent talk that it might be useful or better to revert to a voltage divider. Don’t know where I read it or who wrote it. That’s why I took it into consideration. Just trying to get an overview of the possibilities of the 1-series.

And the temp sensing calibration, yes I saw and liked this. In Anduril I overrode the temp offset for known drivers for not having to recalibrate it after every new flash. And I reflashed a lot since having the progkey.

So yes, I’m pretty stoked when it comes to the 1-series. I will now look deeper into your firmware, especially the test firmware, and cross reference the datasheet to get a better grip on it.

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@TK
I’m not talking lowest moon. I wanted to hint where my interest is and used a brief and thus inaccurate description. I will elaborate below, but this leads away from my real question:

Which function should be connected to which pin?

I need a start to make me a driver that I can use for playing around - without having pins connected blatantly wrong, e.g. unusable.

I got the impression that nothing evolved in the support of this MCU because there was no firmware for it, which might be because there was no driver for it, which again might be because there was no firmware for it…

So tell me what hardware you need at which pin. That’s still my basic question here and I will happily design you a driver and/or troubleshoot firmware.

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Now to PWM.
With the good 7135 ravenclaw I get consistent lowest light with phase correct pwm level 2 at 18kHz. That’s lower than I need or like. I buy them at lcsc.com and bin them for use as 1x7135 at 348-352mA. That makes them incredibly consistent at all pwm levels.

What I care for is about the lower fifth of the ramping table.
Unfortunately I can’t give a picture, as I’m on holiday with a linux laptop, crappy internet and no password for imgur…

#define PWM1_LEVELS 4, 4, 4, 5, 5, 5, 6, 6, 6, 7, 7, 8, 8, 9, 9,10,10,11,11,12,12,13,13,14,14,15,15,16,16,17,17,18,18,19,19,20,20,21,22,22,23,24 ,25,26,26,27,28,29,30,31,32,33…

The lower parts are of course not a curve but a series of linear segments with flat parts and increasing gradient. It’s still either stuttering or gets too bright too fast. I already shortened the lower parts, they were more like 4, 4, 4, 4, 4, 4, 4 when they came out of the python script (after a lot of testing I liked the 7th function best and this leads to a flat start).

I’m still very sure that this will benefit from an increased bitrate. 10-bit alone will be very beneficiary, as it gives 3 additional values inbetween any 2 present ones.

A word of warning, HQ… I’ve built a few drivers around this and in general, I’ve been very pleased. But if you’re going to use these with a clicky switch, you’ll likely need to use an OTC to measure offtime. While the “noinit” trick technically works, I’ve seen it take upwards of 45 minutes for the variables with “noinit” to decay; not very useful for what we need (Mike C has also observed this). For e-switches, this isn’t a problem.

I’ve got a few others around, but that’s the most of it

Yes, I only have plans to start with momentary.
I was designing a new driver for my 2 Yezl Y3, removed the 85, inserted a 20 pin QFNL and liked what I saw :laughing:

The BLF GT used a similar solution… but instead of a linear regulator, it used a buck regulator. The top 15/16ths of the ramp used current control, and the bottom 16th used PWM at 1/16th power. It worked really well.

We tried to use a 7138 chip at one point, but the results weren’t great. It could regulate both ends of its range, but the response curve between wasn’t a useful shape. So that driver design got scrapped.

The Convoy H1 uses the 7138. I’ve got the D4 V2 UI running on it and I love it. But the problem I see with it is the max PWM speed spec is 10 kHz which I’m sure some BLF’ers would complain about.

Do you know what Hank’s 5 amp drivers are using? Op-amp controlling a FET in its linear region?

If it would help get these chips off the ground, I’d be glad to design a great driver around them. But I’m not an expert when it comes to some of this EE stuff so it helps to reference specific chips or at tested designs, etc. I’d do a simple FET + 1x7135 but it seems like people feel that’s not good enough anymore.

Yes and no. I didn’t make firmware for it, but gchart did… so most of the work is already done.

http://www.ghart.com/blf/firmware/

Merging that in is still on my todo list, because I’m slow. I really should do that soon, before my branch diverges too much.

Yeah, extra resolution would definitely be nice for the bottom of the ramp.

I’ve tried a bunch of methods to increase the resolution. Some worked, some didn’t. And some worked on my test host, but failed when installed on another light.

The most effective and reliable methods I’ve tried were the ones which increased resolution in an analog domain. Sometimes digital works, but it’s a lot more prone to failing. This is mostly because the analog components have an inherent noise floor, and no digital solution can increase resolution below that noise floor. When approaching that limit, it’s necessary to lower the noise level in order to make the signal more precise.

Like, let’s say a ramp can go from 1 to 10000, and there is a noise component of +/- 10. Toward the top of the ramp, let’s say it’s at level 9000, it doesn’t really matter if it varies from 8990 to 9010. But toward the bottom at level 100, going from 90 to 110 is probably visible… and even lower at a level of 15, varying randomly from 5 to 25 makes the signal basically unusable.

But give it a second analog path with everything scaled down to 1%, and we get something which can go from 0.01 to 100, with a noise component of +/- 0.1. Now level 15 is a lot more stable, varying only from 14.9 to 15.1.

It’s not always feasible to do this, due to space constraints on the driver… but when possible, it’s almost always the most effective solution.

Er, it might also be worth mentioning that the “noise” isn’t necessarily visible within a single light. Sometimes it’s visible, like the flicker seen at low levels on the KR4, but I’m also talking about the variation within a production run. Produce a thousand items, using a dozen different types of LEDs, and there will be a lot of variation. At the bottom edge of its output range, some items will work great while others don’t light up at all. So I’m mostly trying to stick to solutions which work for the whole batch, not just individual items.

In the case above, that often means that an individual light has a range of 1 to 10000, but the +/- 10 part is a static property of that light. Like… it’s always +5 or it’s always –7. So toward the bottom of its range, I could calibrate the ramp so it looks perfect on my +5 sample, but then when the same code runs on a –7 sample, it looks all wrong. I might set the ramp to start at “4,4,4,5,5,5,6,6,6,7,7”, but on another item it ends up looking like “0,0,0,0,0,0,0,0,0,1,1”.

If it helps at all, the exponent option can be an arbitrary number. Like, if “seventh” is close but not quite right, try giving it 6.9 or 7.03 to fine-tune it.

Anyway, I don’t have answers for Tiny1 circuit design, so I’m not helpful here… but I’d definitely recommend reading through gchart’s code if you haven’t yet.

Hmmm… No.
It’s nice of you being so modest, but it’s not a thing until FSM supports it :wink:

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I totally understand that. I did a lot of measuring, for example to see how different 7135 behave in which condition with which LED and which firmware settings. I settled with a specific hardware and firmware for my bread-and-butter clicky lights. But this includes handpicking not only the 7135 but also all capacitors. The result is totally worth it. I get consistent brightness levels and OTC timing without need for calibrating. But that works as a hobby, for gifting some lights, and just having fun in DIY. Not in a large scale production.

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The fine tuning I did by hand. Wrote me a ramping table test state in Anduril to check the critical parts of the table on a step by step basis. The result puts a smile on my face every time I use this light. Again, this obviously does not work on a production scale.

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Don’t worry. My following post is for the others here. :slight_smile:
But when you ever come to the point that FSM supports the 1-series, I want to be helpful myself, have some drivers ready and provide some testing.

Well yes… and no. The updates haven’t been merged into TK’s repository yet, but the link that TK shared leads you to my updates that integrate 1-Series support into FSM. I have it up and running on Sofirn SC31B (just because I have a few sitting around and it made a decent host) via a PIC-to-ATTYINYx16 adapter board.

I also just threw together a 20mm FET+1 driver and updated programming key. I’m still waiting on the boards to arrive. The programming key is nearly identical to my old one, but I decided it was better to switch around the Gnd and Rst positions (mainly to avoid frying the chip if you reverse the key and also because it works better with PCB layouts).

First, it’s cool to see HQ in here after checks notes 19 months between posts.

I’m not much use in this thread - but I wanted to comment on the 10kHz PWM. Nobody can see that. They can find ways to measure it and show that, but it will never be visible to human eyes. The only issue you’ll run into is if something ends up making a 10kHz tone, which all but the oldest of us will be able to hear. I don’t fully understand why PWM is occasionally audible in lights, but that’s my take. Also, you can get away with a lot slower PWM if the signal’s waveform also has a DC component.

Now I need to get me the hardware.

I’ll go with the 416 xplained nano board after looking at the options. With ~8€ it’s cheap enough not to try my luck with the AliExpress stuff. I will need to upgrade to a newer AVR studio, though.

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One question still:

Which Attiny1616 do I need, MFR or MNR?
Their own datasheets are inconclusive, as they stated the specs differently. The 2020 datasheet version says

ATtiny1616-MNR 16 KB/2 KB 20 20 MHz 1.8V to 5.5V VQFN -40°C to +105°C
ATtiny1616-MFR 16 KB/2 KB 20 16 MHz 2.7V to 5.5V VQFN -40°C to +125°C

Why does the MFR type only support 16MHz?
Mouser/Farnell list both versions as 20MHz. Does the MFR support 20MHz at least below 105C?

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@gchart
I’m not a firmware pro. I can do stuff where I want and need to, it just takes me a lot of time. I’ll be patient and wait for the official integration.

ProgKey: swapping the pins (grd to the center) looks perfect as the pins inbetween, PA1-PA3, might not be as relevant to us and then the routing falls into place almost by itself.

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@Scallywag
time surely flies

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Just for the fun of it: I did some quick-and-dirty board sketching (changing the MCU on existing brds) and it will work out nicely. Yes, the routing is different as we no longer use space under the MCU or between the pins. But there is a lot of space around the MCU now, especially compared to the 85.

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Very exciting developments and many thanks to ToyKeeper, gchart, HarleyQuin for the work! Actually I've been recently working on a driver with 3 channels control just like what TK was talking about, using a buck regulator for most of the range, a separate channel for very low brightness levels, and finally one for FET, though practically speaking the lowest range doesn't need much resolution for brightness levels I think.

Thanks for popping in, loneoceans! I always look forward to seeing what you cook up :slight_smile:

I’m excited for development on low-brightness channels. So far the standard has mostly been a 1x7135 channel, and it does alright. I’d be most excited for an example of how to do it well that others could implement on their future designs

New 20mm FET+1 boards just came in and I assembled one today and threw it in a Sofirn SC31B. So far everything is working great. :+1:

sorry, I hadn’t cleaned flux off yet

I admire your skills and abilities gchart. Well done.

Really nice work!

Outstanding! Any updates? I'm working with Anduril2 now. I assume that's a FET+1.

Well, not a whole lot to update on I guess. Driver works great, and Anduril is running well on it. I haven’t tried Anduril2 yet. Want to make sure it’s fairly stable before I mess with it.